1. Field of the Invention
The invention relates to a process for restoring sulfur-absorbing activity to a spent copper-inorganic porous carrier sorbent for removing sulfur-containing components from hydrocarbons.
2. Description of the Prior Art
U.S. Pat. No. 4,163,708 describes the use of composites of copper compounds and inorganic porous carriers for removing thiol impurities from hydrocarbons to prepare the hydrocarbons for catalytic reforming using platinum or platinum-containing bimetallic catalysts that are poisoned by thiol compounds. The patent teaches that spent composites may be regenerated in a three-stage regeneration process. In the first stage adhered hydrocarbons are stripped from the spent sorbent with a stripping gas. After the stripping the sorbent is subjected to oxidizing conditions to oxidize residual carbon, hydrocarbon, and sulfur compounds on the sorbent. Gas containing a small volume percent of molecular oxygen at 190.degree. C. to 260.degree. C. is a suggested oxidizing medium. The third and final stage of regeneration is to subject the sorbent to a reducing atmosphere to convert copper-sulfur-oxygen moieties on the sorbent to copper oxide/copper metal and sulfur dioxide. The sulfur dioxide is carried away by the reducing gas leaving only the copper oxide/copper on the porous carrier. Nitrogen gas containing a few volume percent hydrogen at 188.degree. C., 5.4 to 6.4 atm is suggested as a reducing medium.
Applicants have found that the regeneration procedure suggested in U.S. Pat. No. 4,163,708 produces less than desired restoration of sorbent activity and lifetime when applied to spent sorbents that do not contain an inherent catalytic oxidizing catalyst, such as chromium or molybdenum oxide, and have been used to remove primarily mercaptans from hydrocarbon feedstocks. With such sorbents it has been found necessary to carry out the reduction stage of the regeneration at much higher temperatures than those suggested in the patent to realize even a minimal level of regeneration. The present invention addresses the problem of regenerating such spent sorbents and provides a novel and unobvious process whereby a substantial portion of the original activity and original lifetime of the sorbent may be restored.